The present invention is in the general field of tire liners for pneumatic tires that have a pressurized air chamber inside the tire and wheel assembly, which is sealed to preclude any pressurized gas from coming between the interior surface of the tire and the tire liner. Specifically, the present invention is an improved means to seal the pressurized air chamber of tire liners that have vee shaped air chambers.
One such tire liner with a vee shaped air chamber is described in Applicant's U.S. Pat. No. 6,568,443. The vee shaped air chamber created by the tire liners described therein, is sealed by means of an “inner tube.” The inner tube referred to is the conventional type of rubber inner tube used in the tire industry. These conventional rubber inner tubes are manufactured in molds that have a round cross section and therefore produce inner tubes that also have a round cross sections, as molded.
Applicant has discovered that there are problems with using “round” inner tubes to seal a “vee shaped” air chamber. The problem is that a conventional round inner tube and a vee shaped air chamber are incompatible, because of their extremely dissimilar shapes. When using a conventional round inner tube to seal a vee shaped air chamber, the conventional round inner tube either (1) “wads” or “bunches” up in the bottom of the vee, the portion of the air chamber closest to the tread, or (2) stretches into the bottom of the vee, thereby placing an extreme tension load on that portion of the conventional round inner tube.
Regarding the “wadding” or “bunching-up” in the bottom of the vee, when using a conventional round inner tube with the seemingly correct diameter and cross section dimensions to seal an intended vee shaped air chamber, the round inner tube simply has to much surface area. Three dimensionally, a conventional “round” inner “tube” is a circular tube and the vee shaped portion of the air chamber is essentially two “cone segments.” A conventional round inner tube with (1) a circumference dimension the same as the perimeter cross section dimension of the intended complete vee shaped air chamber that is parallel with the rotational axis of the tire, and (2) an outside diameter that is the same dimension as the maximum inside diameter of the intended vee shaped air chamber, i.e., the dimension from the bottom of the vee (point closest to the tread) on one side, straight across to the bottom of the vee on the other side, this conventional round inner tube has substantially more surface area than the surface area of the complete vee shaped air chamber. This circumstance causes the “wadding” or “bunching-up” of the excess conventional inner tube in the bottom of the vee shaped air chamber. This is illustrated in FIG. 6. In FIG. 6 there is shown conventional round inner tube 27 with over-all dimensions that correspond to the over-all dimensions of the vee shaped air chamber that it is intended to be used in, as described above, and conventional inner tube 27 is pressurized inside the intended vee shaped air chamber. As the FIG. 6 illustration shows, the conventional inner tube excess “wads” or “bunches” up in the bottom of the vee shaped air chamber creating folds. These folds cause (1) detrimental heat to be generated from the friction of the folds rubbing against each other when in a tire that is being use on the highway and (2) the folds rubbing against each other will rub a hole completely through conventional inner tube 27, which allows pressurized air to now go between the interior surface of the tire and the tire liner. When the pressurized air is allowed to get between the interior surface of the tire and the tire liner through the hole rubbed in conventional inner tube 27, this equalizes the air pressure force on both sides of the tire liner. When the air pressure is equal on both sides of a tire liner inside a tire, the tire liner abrades the interior surface of the tire, damaging the tire. Because there is no pressure differential to press the tire liner against the interior surface of the tire and keep it from rubbing against the interior surface.
A conventional round inner tube with over-all dimensions that correspond to the over-all dimensions of a vee shaped air chamber that it is intended to be used in, does not provide a functional means of sealing a vee shaped air chamber because of the inherent, insurmountable surface area problem that generates detrimental heat and ultimately holes in the conventional round inner tube. Thereby defeating its sole purpose of sealing the air chamber.
Attempts to eliminate the “wadding” and “bunching-up” in the bottom of the vee problem set forth above by using a conventional round inner tube with over-all dimensions that are less than the over-all dimensions of the vee shaped air chamber that it is intended to be used in, the conventional round inner tube now having less surface area than the intended complete vee shaped air chamber, creates an extreme tension load problem.
The “vee shape” of the air chamber causes a round inner tube with over-all dimensions that are less than the over-all dimensions of the intended complete vee shaped air chamber, to “thrust” out of the vee shaped air chamber toward the wheel during initial pressurization. Which ultimately results in an extreme tension load being placed on the conventional round inner tube. This problem is illustrated in FIGS. 7, 8 and 9.
In FIG. 7 there is shown a cross section of a conventional round inner tube 25 as molded. In FIG. 7 there is also shown a cross section of a tire and wheel assembly that includes a tire liner that creates a vee shaped portion of the complete air chamber. And in the air chamber of this assembly is conventional inner tube 25 which has over-all dimensions that are less than the over-all dimensions of the vee shaped air chamber and conventional inner tube 25 is unpressurized.
FIG. 8 shows the same tire and wheel assembly cross section that is shown in FIG. 7, except that now conventional inner tube 25 has begun to have pressurized air introduced into it. This initial pressurization period, when the pressure in conventional inner tube 25 is approximately two (2) or three (3) PSI, is what causes the “thrusting” problem. Two (2) or three (3) PSI is not enough air pressure force to hold conventional inner tube 25 stationary against the vee shaped surface portion of the air chamber to counteract the inherent characteristic of the vee shape to eject a round inner tube expanding in it. Two (2) or three (3) PSI is however, enough air pressure force to cause conventional inner tube 25 to thrust out of the vee shaped air chamber toward the wheel. FIG. 8 illustrates this thrusting toward the wheel problem during initial pressurization. FIG. 8 shows during initial pressurization, with approximately two (2) or three (3) PSI in conventional inner tube 25, conventional inner tube 25 has pulled away from the bottom of the vee shaped air chamber, i.e., the part of the air chamber closest to the tire tread, as shown in FIG. 7, and has thrust toward the wheel.
As the air pressure in conventional inner tube 25 is increased beyond the initial pressurization pressure, conventional inner tube 25 now begins to stretch back toward the bottom of the vee shaped air chamber. And when conventional inner tube 25 is pressurized to the required pressure for tire liner applications intended for highway use, conventional inner tube 25 has stretched all the way back to the bottom of the vee shaped air chamber. This is illustrated in FIG. 9 which shows the progression of conventional inner tube 25 as it stretches back toward the bottom of the vee shaped air chamber as the air pressure is increased beyond the initial pressurization pressure. This stretching places the portion of conventional inner tube 25 that has stretched all the way back to the bottom of the vee, under an extreme tension load.
The tension load illustrated in FIG. 9 becomes a dynamic, cyclical tension load when the tire is put to uses on a vehicle. When under the load between the axel and the ground, that portion of conventional inner tube 25 under an extreme tension load, now moves back toward the wheel. And therefore back toward a neutral load thereby significantly reducing the tension load. As the tire rotates and that portion of conventional inner tube 25 is no longer between the axel and the ground, it move back to its normal pressurized position, restoring the tension load. Cycling like this for every revolution of the tire. This cycling during highway use generates so much heat that it causes the portion of conventional inner tube 25 under this extreme tension load to fail and the tire liner portion in contact with it to be damaged.
A conventional round inner tube with over-all dimensions that are less than the over-all dimensions of a vee shaped air chamber that it is intended to be used in, does not provide a functional means of sealing a vee shaped air chamber because of the inherent, insurmountable extreme tension load problem that results from the conventional round inner tube having to stretch into the bottom of the vee shaped air chamber.